1
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Find the product 4 x ( -5 ) x ( - 7.5)

2
00:00:07,400 --> 00:00:10,667
Just multiply 3 numbers here, some are positive

3
00:00:10,667 --> 00:00:13,467
some are negative. We can do it in any order

4
00:00:13,467 --> 00:00:18,533
Lets start with 4 x -5, and then we will multiply

5
00:00:18,533 --> 00:00:22,867
what ever we get with - 7.5

6
00:00:22,867 --> 00:00:36,600
so lets write it again 4 x ( -5 ) x ( - 7.5)

7
00:00:36,600 --> 00:00:38,867
The first thing we need to realise is a

8
00:00:38,867 --> 00:00:44,533
(+) x (+) = +, and a (+) x( -) = - or (-) x (+) = -

9
00:00:44,533 --> 00:00:46,974
(- ) x ( -) = +. If we multiply two numbers

10
00:00:46,974 --> 00:00:50,067
with same sign, we get a + answer and if we

11
00:00:50,067 --> 00:00:52,467
multiply two numbers with different sign

12
00:00:52,467 --> 00:00:58,733
we get a - answer.4 x 5 = 20

13
00:00:58,733 --> 00:01:03,314
we have a (+) x (-) ,two numbers with different sign

14
00:01:03,314 --> 00:01:07,895
so we will have a -

15
00:01:07,895 --> 00:01:16,301
it becomes -20 x - 7.5.

16
00:01:16,301 --> 00:01:19,533
we will figure what that is, I will work out what

17
00:01:19,533 --> 00:02:05,533
is 20 x 7.5 = 150.0

18
00:02:05,533 --> 00:02:08,600
now we think if it is + or -

19
00:02:08,600 --> 00:02:12,818
we have a (-) x (-), they are the same sign

20
00:02:12,818 --> 00:02:16,975
the answer will be +.

21
00:02:16,975 --> 99:59:59,999
so the answer is + 150.0